Controller for alternating-current circuits.



N0. 644,05l. Patented Feb. 27, I900. E. J. BERG.

CONTROLLER FOR ALTERNATING CURRENT CIRCUITS.

(Application med'oct. 11, 1899.)

(No Modal.)

Jnvenbor, Ernst/J. Berg. mulg-$rwk m: uonms mas col, FNOTD-LlTHU" wxsumm'on u c UNITED STATES PATENT OFFEtcE.

ERNsT J. BERG, or sCnEN TAD NEW YORK, ASSIGNOR TO THE GENERAL ELECTRIC CoMPANY, on NEW YCRK.

CONTROLLEFi FOR ALTERNATlNG-CURRENT CIRCUITS;

SPECIFICATION forming part of Letters Patent No. 644,051, dated February 27, ieoo. Application filed 0ctober11,l899. Serial. No. 733,246. (No model.)

To aZZ whom it may concern:

Be it known that I, ERNsT J. BERG, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Means for Controlling Alternating-Current Circuits, (Case No. 1,150,) of which the following is a specification.

It has been found by experience that alternating-current arcs are in general more difficult to extinguish than those occasioned by direct current. This difliculty assumes considerable proportions when it is necessary to open a closed alternating-current circuit or circuits at frequent intervals, as is the case in controlling alternating-current motors and other translating devices. The efiect of the electric arc upon the switching-contacts used in controlling electric circuits is very detrimental, since the metal forming the contact-surfaces is fused, burned, and otherwise distorted, thus making good Contact between the surfaces impossible, and so after a short time rendering the switches or controllers employed unfit forfurther service. My present invention aims to avoid this difficulty by doing away, so far as possible, with its cause, and this purpose is accomplished by reducing the current to be broken to a minimum at the time the break is to take place, the current being so far reduced that the resulting are or arcs are insignificant in effect.

The details of my invention will be better understood by reference to the following description, taken in connection with the accompanying drawing, While its scope will be particularly pointed out in the Claims appended hereto.

In carrying out myiuven tion I provide each alternating-current circuit or circuits to be manipulated with an inductance-coil in series therewith or otherwise connected, so as to set up a reactive electromotive force in the line. Cooperating with each inductance-coil is a plate of metal arranged to be brought into close mutual inductive relation to the inductance device during the period when the alternating circuit is closed and in operation and to be moved out of inductive relation immediately prior to the instant when the circuit is to be broken. The plate of metal acts as a short-circuited secondary and reduces the self-induction of the inductance device to insignificance when in close mutual inductive relation thereto and produces the reverse effect when out of the influence of the inductive device. The effect of this relationship is to cause a large reactive electromotive force to be induced in the alternating-current circuit immediately before the circuit is broken, thus reducing the current to a minimum at the time of breaking, and so rendering the resulting arcing insignificant.

In the drawing I have shown my invention as applied to a controller for operating a multiphase ind notion-motor of the threephase type. The terminals of the three-phase supply-circuit are indicated at 1, 2, and 3, and these terminals are connected, respectively, to contact-fingers 4: 5 6 of a controller. A developed view of the contacts on the cylinder of the controller is shown on the right-hand portion of the drawing. The contact-fingers 4 5 6 cooperate with contacts 7 8 9 on the controller-cylinder,- these contacts being crossconnected to other contacts 10, 11, and 12, respectively. The latter set of contacts connects the supply-terminals to the terminals of the motor (represented at M) by means of the contact-fingers 13, 14, and 15. As soon as the controller is moved forward from its off position the connections thus described are made and are maintained during the subsequent operations of the controller until its final return to the off position. In series with each line of the primary supply-circuit for the motor M is an inductance-coil, (indicated at 16.) Each coil is preferably provided with a core, the ends of which are located in proximity to the surface of the controller-cylinder. The latter is provided with three curved plates of heavy metal secured to its cylindrical surface and extending partially about its circumference. These plates are indicated at 17 and are arranged to be out of proximity to the cores of the inductance-coils 16 at the time the terminals 1, 2, and 3 are first connected to the con facts 7, 8, and 9,'but to be brought opposite to the cores upon a further forward motion of the controller-cylinder.

The secondary of the motor M is shown with a Y-connected winding leading to resistances feet upon the circuit.

R R R These resistances are divided into sections and are connected to suitable contactfingers r s t u, r s, &c. These contact-fingers cooperate with contacts, (indicated generally at 0,) which contacts serve to cut in and out the successive sections of the resistances R R R as will readily be understood without further explanation.

In the operation of the embodiment of the invention thus described the first step is to move the controller forward, thus connecting the primary of the motor in circuit to the terminals l 2 3 through the inductance-coils 16, which at this time have their full reactive efcontroller-cylinder brings the heavy plates of metal 17 opposite the cores of the inductancecoils 16. These plates of metal then act as short-circuited secondaries and serve to cut down the self-induction of the windings of the inductance-coils to a minimum in a manner Well understood. A further motion of the controller-cylinder then closes the secondary of the motor M through the resistances R R R while upon still further moving the controller these resistances are gradually cut out step by step until the secondary winding is short-circuited upon itself.

Upon the reverse operation of the controller these steps are performed in the reverse order, resistance being gradually inserted in the secondary of the winding, the secondary circuit then being broken. The metal plates are then removed from proximity to the cores of the inductance-coils, thus setting up a counter electromotive force of self-induction in the primary circuit, and so cutting down the current in the primary circuit to a min i mum. At this point the primary circuit is broken; but owing to the small amount of current then flowing the resulting arcs have little, if any, effect upon the contacts and contact-fingers between which the arcing takes place.

Although I have shown my invention in connection with a regulation of an inductionmotor, it will readily be understood that its useful features are not at all limited to use in-that connection, but are applicable in many other cases where alternating currents are to be controlled by making and breaking circuits.

What I claim as new, and desire to secure by Letters Patentof the United States, is-

Further motion of the 1. The combination of an induction-motor, a resistance in the secondary of the motor, an inductance device in the primary leads of the motor,and a controller for varying the amount of said resistance and for varying the self-induction of said device.

2. The combination of an induction-motor, a resistance in the secondary of the motor, an inductance-coil in the primary leads of the motor, and a controller for asynchronously varying the amount of said resistance and the self-induction of said coil.

3. The combination of a controller for an alternating-current circuit, an inductancecoil in said circuit and a short-circuited secondary arranged to be put in close inductive relation to said inductance-coil at all times other than when the controller is about to break or has broken said circuit.

4. The combination of a controller for an alternating-current circuit, an inductancecoil in said circuit and a short-circuited secondary carried by said controller and ar ranged to be put out of close inductive relation to said inductance-coil when the controller is in position to break said circuit.

5. The combination of a translating device, an inductance -coil, acontroller provided with contacts, and cooperating contact-fingers for connecting said translating device in circuit and for varying the energy supplied to the same, and means for varying the reactance factors of said inductance-coil without varying its number of effective turns.

6. The combination of a translating device, an inductance-coil, a controller for said translating device, means operated by said controller for increasing the reactance factor of said inductance-coil as the controller is moved to the off position and for maintaining said factor at a minimum at other positions of the controller.

7. In a switching means for alternating-current circuits, the combination of a resistancevarying means, and asynchronously and dependently operated means for introducing a high reactance electromotive force into said circuit.

In'witness whereof I have hereunto set my hand this 10th day of October, 1899.

ERNST J. BERG.

WVitnesses:

BENJAMIN B. HULL, MABEL E. JAooBsoN. 

